When light is totally reflected on the surface of a medium, electromagnetic theory analysis for light indicates that an electromagnetic field also exists in an optically thinner medium, total-reflection light generates a small shift in side direction relative to the point of incidence. Because the shift is discovered by Goos and Hanchen, the shift is called Goos-hänchen shift, G-H shift for short. Along with the discovery of the Goos-hänchen shift, the research on a Goos-hänchen shift generation mechanism becomes a hot issue.
There are two generally-accepted opinions at present: according to the opinion I, the Goos-hänchen shift is generated because different monochromatic planar light components in incident light have different reflection-induced phase shifts, and a reflected light beam is formed by superimposing of reflected planar light components, so that a longitudinal shift is generated in the reflected light beam; and according to the opinion II, generation of the Goos-hänchen shift is closely related to an evanescent field in the optically thinner medium, and according to the nature of energy flow in the evanescent field, the relationship between the Goos-hänchen shift and the energy flow in the evanescent field is derived from the view of energy conservation. However, the Goos-hänchen shift cannot be effectively regulated based on the above opinion II, so that the application of the Goos-hänchen shift in the fields of optical sensors, all-optical switches, light beam shift modulation devices, and the like is limited.